The present invention relates generally to a valve for providing pressure relief in response both to attitude and pressure conditions, and relates more particularly to such a valve adapted for implantation to relieve intracraneal pressure in treatment of hydrocephalus.
Devices for draining ventricular fluid in cases of hydrocephalus have been available for some time. An early example of such a device is shown in my U.S. Pat. No. 2,969,066, issued Jan. 24, 1961. These devices essentially are pressure responsive valves which open upon the occurrence of a predetermined gradient across the valve to allow flow of cerebrospinal fluid sufficient to lower the ventricular pressure to the desired level.
Since the typical cerebrospinal fluid shunt valve responds only to the fluid pressure gradient, such valves are unable to accommodate changes in attitude of the patient if the valve discharges into a catheter of considerable length such as a peritoneal catheter, since the pressure at the upper end of the catheter into which the valve discharges in a pressure gradient responsive valve controls the actual pressure relief achieved. Accordingly, such a valve implanted in a patient's head and utilizing a lengthy peritoneal catheter would function normally only when the patient were in an upright position, but would not produce the desired relief when the patient were in the horizontal position because of the substantial increase in the pressure at the discharge port of the valve.